Intervertebral device having expandable endplates

ABSTRACT

An intervertebral implant having an endplate that can be slidably expanded following its placement in the intervertebral space. The endplate comprises a pair of planks that are slidably received within respective recesses of a base portion of the endplate. During insertion of the implant into the intervertebral space, the planks are set in a contracted position within respective recesses of a base portion of the endplate. This provides the implant with a relatively small profile that is suitable for MIS procedures. Once the implant has been inserted, the planks are slid outward from the recesses to an expanded position that increases the footprint of the implant endplate. This expansion increases the stability of the implant.

CONTINUITY DATA

This application claims priority from co-pending U.S. Ser. No.13/281,833, filed Oct. 26, 2011, to Stad, entitled “IntervertebralDevice Having Expandable Endplates”, the specification of which isincorporated by reference in its entirety, which claims priority fromU.S. Ser. No. 11/694,524, filed Mar. 30, 2007, to Stad, entitled“Intervertebral Device Having Expandable Endplates”, (Now U.S. Pat. No.8,137,401), the specification of which is incorporated by reference inits entirety.

BACKGROUND OF THE INVENTION

The leading cause of lower back pain arises from rupture or degenerationof lumbar intervertebral discs. Pain in the lower extremities is causedby the compression of spinal nerve roots by a bulging disc, while lowerback pain is caused by collapse of the disc and by the adverse effectsof articulation weight through a damaged, unstable vertebral joint. Oneproposed method of managing these problems is to remove the problematicdisc and replace it with a prosthetic disc that allows for the naturalmotion between the adjacent vertebrae (“a motion disc”).

Since first generation motion discs were inserted anteriorly, the sizeof the disc's endplate did not hinder the insertion technique and so wasessentially equal to the size of the vertebral endplates opposing themotion disc. However, later generation motion discs seek to insert themotion disc from the posterior or posterolateral directions. Thesemethods of insertion seek to minimize the size of the portal throughwhich the motion disc is inserted. However, such a minimized profile mayunacceptable reduce the size of the prosthetic endplate.

Thus, it is an object of the present invention to provide a motion discthat can be inserted from the posterior or posterolateral directions andthat has a relatively large endplate footprint.

US2005/0060037 (Michelson) describes an interbody spinal fusion implanthaving an expandable height and interlocking side walls to maintain theincreased height of the implant. More particularly, it describes athreaded fusion cage having adjustable lordosis.

US2005/0071007 (Malek) describes intervertebral disc prostheses thathave adjustable disc heights, that are readily converted into fusionprostheses and that provide a range of motions that effectively mimicthe natural range of motions of a spinal disc.

US2005/0256576 (Moskowitz) describes an total artificial expansible dischaving at least two pairs of substantially parallel shells, which movein multiple directions defined by at least two axes, is disclosed.Several methods for implanting the total artificial expansile disc arealso disclosed. The total artificial expansile disc occupies a spacedefined by a pair of vertebral endplates. An expansion device moves thepairs of shells in multiple directions. A core is disposed between thepairs of shells, and the core permits the vertebral endplates to moverelative to one another.

US2005/0209698 (Gordon) describes an artificial functional spinal unitincluding an expandable intervertral implant that can be inserted via aposterior surgical approach and used with one or more facet replacementdevices to provide an anatomically correct range of motion. Lordotic andnon-lordotic expandable, articulating implants and cages and methods ofinsertion are also described. Gordon further describes an advancingelement that can increase height.

US2005/0197702 (Coppes) describes a fixed size endplate having aninflatable middle. Coppes relates to an artificial intervertebral discfor placement between adjacent vertebrae. The artificial intervertebraldisc is preferably designed to restore disc height and lordosis, allowfor a natural range of motion, absorb shock and provide resistance tomotion and axial compression. Furthermore, the intervertebral disc maybe used in the cervical, the thoracic, or the lumber regions of thespine. The artificial intervertebral disc may include either singularlyor in combination: an interior at least partially filled with a fluid; avalve for injecting fluid into the interior of the disk; a centralregion having a stiffness that is preferably greater than the stiffnessof the outer regions thus enabling the disc to pivot about the centralregion. The central pivot may be formed by a center opening, a centralchamber, an inner core or a central cable.

WO2006058281 (“Glenn”) discloses a spinal implant to be inserted betweentwo vertebra to support and stabilize adjacent vertebra and allow forphysiological motion. The invention includes an implantable device tosupport the vertebrae, and a minimally invasive method for inserting anddeploying the device within the intervertebral space

SUMMARY OF THE INVENTION

The present invention relates to an intervertebral implant having anendplate that can be expanded following its placement in theintervertebral space.

In a first embodiment, the endplate comprises a pair of planks that areslidably received within respective recesses of a base portion of theendplate. During insertion of the implant into the intervertebral space,the planks are set in a contracted position within respective recessesof a base portion of the endplate. This provides the implant with arelatively small profile that is suitable for MIS procedures. Once theimplant has been inserted, the planks are slid outward from the recessesto an expanded position that increases the footprint of the implantendplate. This expansion increases the stability of the implant.

Therefore, in accordance with the present invention, there is providedan intervertebral implant device having an expandable endplate, theendplate comprising:

-   -   a) a first base portion having an outer surface adapted for        bearing against a natural endplate, an inner surface, first and        second side surfaces extending between the outer and inner        surfaces, a first cutout opening onto the outer surface and the        first side surface and forming a first recessed surface, and    -   b) a first plank slidingly receivable within the first cutout        and adapted to translate across the first recessed surface.

DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of an endplate of the present inventionhaving its second base portion removed to fully expose the plankstherein.

FIG. 2 is a perspective view of an endplate of a motion disc of thepresent invention, wherein the planks are in a contracted position.

FIG. 3 is a perspective view of an endplate of a motion disc of thepresent invention, wherein the planks are in an expanded position.

FIG. 4 a is a perspective view of a pair of opposed endplates of thepresent invention, wherein the planks are in a contracted position.

FIG. 4 b is a perspective view of the pair of opposed endplates of FIG.4 a, wherein the planks are in an expanded position.

FIG. 4 c is a perspective view of the pair of opposed endplates of FIG.4 b having intervertebral struts placed therebetween.

FIG. 5 discloses a parallelogram-type endplate having pivoting planks ina contracted state.

FIG. 6 discloses a parallelogram-type endplate having pivoting planks inan expanded state.

FIG. 7 discloses a fan-type endplate having pivoting planks in acontracted state.

FIG. 8 discloses a fan-type endplate having pivoting planks in anexpanded state.

DETAILED DESCRIPTION OF THE INVENTION

Now referring to FIG. 1, there is provided an intervertebral prostheticdevice having an expandable endplate, comprising:

-   -   a) a first base portion 1 having an outer surface 3 adapted for        bearing against a natural endplate, an inner surface 5, first 7        and second 9 side surfaces extending between the outer and inner        surfaces, a first cutout 11 opening onto the outer surface and        the first side surface and forming a first recessed surface 13,        and a second cutout 15 opening onto the outer surface and the        second side surface and forming a second recessed surface 17,    -   b) a first plank 19 slidingly receivable within the first cutout        and adapted to translate across the first recessed surface, and    -   c) a second plank 21 slidingly receivable within the second        cutout and adapted to translate across the second recessed        surface.

In this embodiment, the first and second cutouts are joined by a thirdrecessed surface 22 in the outer surface of the first base portion.

The first plank of this embodiment has a substantially T shape having afirst shaft portion 23 having an first outer end portion 25, a firstinner end portion 27 and a first pair of flexible arms 29 extending fromthe outer end portion

During insertion, the first pair of flexible arms is received in thefirst cutout in a contracted position (not shown) in order to minimizethe profile of the endplate. The contraction of the arms is caused bythe flexible arms bearing against an inner rim 31 of the cutout. Afterinsertion, the plank is slid outwards from the cutout (as shown in FIG.1), and the first pair of flexible arms becomes free of the bias of theinner rim of the cutout, and thereby expands. Likewise, the second plankof this embodiment also has a substantially T shape having a secondshaft portion 33 having a second outer end portion 35, a second innerend portion 37 and a second pair of flexible arms 39 extending from theouter end portion. It behaves substantially similarly to the first plankduring insertion and expansion, sliding from a contracted position to anexpanded position.

The two planks are designed to interweave with one another in both thecontracted and expanded positions. The endplate is designed so that thefirst outer end portion of the first plank is slidably received in arecess 41 in the second inner end portion of the second plank. In thecontracted state, the first outer end portion of the first plank isnearly fully received in a recess in the second inner end portion of thesecond plank. After expansion, a first flange 43 extending from thefirst outer end portion of the first plank bears against a second flange45 extending from the second outer end portion of the second plank,thereby preventing further outward movement of the planks so as topartially stabilize the expanded position construct.

Also in the expanded position, the end portions of the freed flexiblearms may now bear against the first side surface of the base portion soas to prevent retraction of the arms back into the cutouts and tostabilize the expanded position construct.

Now referring to FIG. 2, the endplate of FIG. 1 may further comprise:

-   -   c) a second base portion 51 connected with the first base        portion and having an inner surface 53 opposing the outer        surface 3 of the first base portion to enclose the first plank        within the first cutout and the second plank within the second        cutout. The purpose of the second base portion is to prevent the        planks from moving out of the cutouts, thereby partially        stabilizing the expanded position construct.

The coupling of the first and second base portions produces a sleeveinto which the planks are slidably received. Therefore, in accordancewith the present invention (and now referring to FIG. 3), there isprovided an intervertebral prosthetic device having an expandableendplate, the endplate comprising:

-   -   a) a sleeve 61 having an outer surface 63 adapted for bearing        against a natural endplate, an inner surface 65, first 67 and        second side 69 surfaces extending between the outer and inner        surfaces, a first recess 71 extending into the sleeve from the        first side surface, and a second recess extending into the        sleeve from the first side surface,    -   b) a first plank 73 slidably received in the first recess of the        sleeve, and    -   c) a second plank 75 slidably received in the second recess of        the sleeve.

In most embodiments, the inner surface of the endplate has a functionalfeature thereon. Now referring to FIG. 3, if the implant is anarticulating motion disc, then the functional feature is an articulationsurface 77. If the implant is a cushion-type motion disc, then thefunctional feature can be an expandable bag that is attached to each ofthe inner surfaces of the opposed endplates and then filled with acompliant material after insertion.

Now referring to FIG. 3, there is provided is a perspective view of anendplate of FIG. 2, wherein the planks are in an expanded position.Extending from the outer end portion of the T shaped plank is handle 76.After insertion, these handles are pulled outwardly to expand theendplate.

Now referring to FIG. 4 a, if the implant is to be a fusion cage, thenit is desirable to use two endplates 80 having sleeves to encloseplanks, shown here in their contracted position. FIG. 4 b shows theendplates provided in an opposed relationship with their planks in anexpanded position. FIG. 4 c is a perspective view of the pair of opposedendplates of FIG. 4 b having intervertebral struts 81 placedtherebetween. In FIGS. 4 a-4 c, the functional feature upon the innersurface 82 of the endplate is adapted to connect to a first load-bearingstrut. In these fusion cage embodiments, the embodiment may furtherinclude a second functional feature adapted to connect to a secondload-bearing strut. In FIGS. 4 a-4 c, the functional feature is arecessed groove 83.

In fusion-type embodiments, it may be desirable to provide endplateshaving throughholes extending between the inner and outer surfaces ofthe endplates so as to accommodate fusion. This may be accomplished byproviding holes through the first and second base portions of eachendplate. These througholes are adapted to provide bone growththerethrough in order to facilitate the fusion of the disc space.

In some fusion-type embodiments (not shown), the struts are providedwith an angle, of typically between about 5 and about 15 degrees. Theseangled struts may be used to provide the endplate with a lordoticorientation.

In some embodiments of the present invention, the endplate is madeexpandable by providing pivoting planks within a sleeve.

Now referring to FIGS. 5 and 6, there is provided an intervertebralprosthetic device having an expandable endplate, the endplatecomprising:

-   -   a) a sleeve 91 having an outer surface 93 adapted for bearing        against a natural endplate, an inner surface, first and second        side surfaces extending between the outer and inner surfaces, a        first recess extending into the sleeve from the first side        surface, and a second recess extending into the sleeve from the        first side surface,    -   b) a first plank 94 slidably received in the first recess of the        sleeve and pivotally connected to the sleeve, and    -   c) a second plank 95 slidably received in the second recess of        the sleeve and pivotally connected to the sleeve.

In this particular embodiment, the sleeve itself has a substantiallyparallelogram shape comprising a first acute corner 97 and a secondopposite acute corner 99. The first plank is pivotally connected to thesleeve in the first acute corner of the sleeve, and the second plank ispivotally connected to the sleeve in a second opposite acute corner ofthe sleeve.

In use, the endplates are inserted into the disc space in a contractedposition. Once the endplates are in the disc space, the planks are swungout of their respective recesses to their expanded positions. In thisparticular embodiment, the expanded configuration forms a D-shapedfootprint, thereby mimicking the footprint of the natural vertebralendplate.

Now referring to FIGS. 7 and 8, there is provided an intervertebralprosthetic device having an expandable endplate, the endplatecomprising:

-   -   a) a first outer plank 101 having an outer surface 103 adapted        for bearing against a natural endplate, and an inner surface,        and a first throughhole extending between the outer surface and        the inner surface thereof,    -   b) a second outer plank 105 having an outer surface adapted for        bearing against a natural endplate, and an inner surface 107,        and a second throughhole extending between the outer surface and        the inner surface thereof,    -   c) an inner plank 109 disposed between the inner surfaces of the        outer planks and having a third throughhole extending        therethrough, and    -   d) a pivot pin 111 extending through each of the throughholes to        pivotally connect the planks.

As shown in FIGS. 7 and 8, the pivot pin extends substantially through amidportion 113 of each plank.

In use, the endplate is inserted into the disc space in a contracted,aligned position. Once the endplate is in the disc space, the planks arerotated about the pivot pin from their respective aligned positions totake their expanded positions. In this particular embodiment, theexpanded configuration forms a D-shaped footprint, thereby mimicking thefootprint of the natural vertebral endplate.

In some embodiments, at least some of the plank surfaces are recessed toprovide nesting with an adjacent plank. This nesting feature not onlycan allow the individual surfaces of the adjacent planks to combine intoa single planar surface, it also locks the planks into their desiredorientation.

Preferably, the outer surface of an endplate of the present inventioncan be either flat, curved or domed to match the natural vertebralendplate. Alternatively, the geometry of the inferior surface can bedesigned so that it will match the shape of the patient's vertebralendplate after the vertebral endplate has been modified by anendplate-shaping instrument. In addition, the outer surface of thisendplate can further comprise features to promote and secure initialfixation and bony ingrowth including, but not limited to, spikes, keels,teeth, projections (such as dovetails), recesses (such as grooves),throughholes and porous coatings.

We claim:
 1. A method comprising the steps of: a) inserting into a discspace an intervertebral implant device having an expandable endplate,the endplate comprising: a) a first base portion having an outer surfaceadapted for bearing against a natural endplate, an inner surface, firstand second side surfaces extending between the outer and inner surfaces,a first cutout opening onto the outer surface and the first side surfaceand forming a first recessed surface, and b) a first plank slidinglyreceivable within the first cutout and adapted to translate across thefirst recessed surface, wherein the first plank has a first shaftportion having a first outer end portion, a first inner end portion anda first pair of flexible arms extending from the outer end portion, andwherein the plank is set in a contracted position within the firstrecessed surface, and b) sliding the plank outward from the recessedsurface to an expanded position.
 2. The method of claim 1 wherein thebase portion further comprises a second cutout opening onto the outersurface and the second side surface and forming a second recessedsurface, and wherein the endplate further comprises: c) a second plankslidingly receivable within the second cutout and adapted to translateacross the second recessed surface.
 3. The method of claim 2 wherein thefirst and second cutouts are joined by a third recessed surface in theinner surface of the first base portion.
 4. The method of claim 3wherein the first plank has a substantially T shape having a first shaftportion having a first outer end portion, a first inner end portion anda first pair of arms extending from the outer end portion.
 5. The methodof claim 1 wherein the expanded position increases a footprint of theimplant device.
 6. The method of claim 5 wherein the first pair offlexible arms are receivable in the first cutout in a contractedposition.
 7. The method of claim 5 wherein the first pair of flexiblearms bear against the first side surface in an expanded position.
 8. Themethod of claim 4 wherein the second plank has a substantially T shapehaving a second shaft portion having a second outer end portion, asecond inner end portion and a second pair of arms extending from theouter end portion.
 9. The method of claim 8 wherein the second pair ofarms are flexible.
 10. The method of claim 9 wherein the second pair offlexible arms are receivable in the second cutout in a contractedposition.
 11. The method of claim 9 wherein the second pair of flexiblearms bear against the first side surface in an expanded position. 12.The method of claim 8 wherein the first outer end portion of the firstplank is received in a recess in the second inner end portion of thesecond plank.
 13. The method of claim 1 further comprising: c) a secondbase portion connected with the first based portion and having an innersurface opposing the inner surface of the first base portion to enclosethe first plank within the first cutout.
 14. The method of claim 13wherein the second base portion further has an outer surface having anarticulation surface thereon.
 15. The method of claim 13 wherein thesecond base portion further has an outer surface having a first recessadapted for connection to a first load-bearing strut.
 16. The method ofclaim 15 wherein the load-bearing strut has an angle.